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ReSAC participation in the flood risk management in Bulgaria

ReSAC was a subcontractor in a project related with the flood risk management using satellite information for a pilot region in Bulgaria. The project goals were to model high water level and to detect flooded area based on satellite images.

In the autumn of 2007 ReSAC participated in a pilot project for developing of a methodology and modeling application for forecasting of potential losses from Iskar river floods for the region of Novi Iskar, Bulgaria.

The main contractor of the project was Agency for Sustainable Development and Eurointegration – ASDE with subcontractors Remote Sensing Application Center – ReSAC and National Institute for Meteorology and Hydrology – NIMH.

The main beneficiary of the project is Sofia Municipality and the project was fulfilled with the coordination of the State Agency for Information Technologies and Communications – SAITC.

The pilot project is in relation with:

- Municipal program “Local Agenda 21”; – Annual program for participation of Bulgaria in the decision making process of EU (2007) – Scientific-applicable task of SAITC for risk management; – Bulgarian-French project “BULGARISK” for application of satellite images for risk management; – Pilot project for monitoring on the base of remote sensing, including fast-track services; – GMES Program; – URBAN-NET, FP6.

In the past couple of years ASDE and ReSAC are introducing and implementing in Bulgaria the good European practices in the area of risk management using satellite information. As a non-profit organizations ASDE and ReSAC are cooperating with numerous governmental, NGO, scientific and private organizations by forming public-private partnerships – PPP in order by optimal cooperation to fulfill better the tasks. The present project is an example of such partnership. The development of a methodology for estimating potential losses from floods aims not only to respond to the current European requirements, but also to respond the real practical problems, which occur in the area of Sofia Municipality during the floods in 2005 and 2006.

The project had the following tasks: – Developing of a methodology for flood simulation and analyses of potential losses, prediction of flooded area along Iskar river in the Novi Iskar region; – Integration of GIS information with satellite images; – Developing of a methodology for metadata for satellite images; – Testing of different DEMs for flood modeling.

The project followed the main principles from the new European directive for floods issued on 23th October 2007. The aim of the EU Flood Directive is to reduce and manage the risks that floods pose to human health, the environment, infrastructure and property. According to the EU Flood Directive, Member States will have to reduce flood risk for those areas where the risk is deemed significant. This is done by first determining the extent of flood risk (through flood hazard mapping and flood risk mapping). Consequently, objectives for flood risk reduction have to be established, as well as the measures that will be taken to reach these objectives. These are laid down in flood risk management plans.

The project shows also some of the GMES services for provision of information products for floods based on earth observation technologies.

The project area is of about 80 and covers part of the Iskar river watershed in the Sofia Valley.

The project was focused on two big floods which occur in June and August 2005. In order to analyse the flooded area 4 satellite images were used:

Details Satellite
Date 19/08/2004 16/06/2005 30/06/2005 12/08/2005
Spatial resolution 5 m 1 m 23 m 23 m

Map of the flooded areas: June-August 2005

Because the satellite images are used as a base for creation of different information products it is very important information for the source and processing of the images to be available, or so called metadata.

ReSAC, using part of the methodology of JRC/EC for metadata for satellite images created a modified templates by which to describe the processed images. These metadata include information about the raw image, geometric processing performed, and information about the GCPs, ICPs and orthorectification accuracy as well as information for the final product delivered.

The developed methodology is open for new modifications based on the new European rules for exchange and maintenance of spatial information, which is to be accepted in the next years.

Based on topographic maps and satellite images different GIS layers were created which to be used in the flood modeling such as:

- road network; – ditches and dikes; – river and channel network; – DEM in scale 1:5000

In order to model hydraulically the water flow the MIKE 11 software was used. The model was fed with various hidro-meteorological information from the National Institute for Meteorology and Hydrology: water levels, water quantities; meteorological data.

Because the DEM was prepared from topomaps which were not updated in the previous 15 years several cross sections were measured with precise instruments in the flooded area in order to obtain information for the riverbed and detailed information for the relief of the flood plain.

The model results were compared with the real flooded area digitized from the satellite images and this information was used to assess the types of land use flooded in June and August 2005.

Comparison between the model result and real flooded area based on satellite images (Ikonos and IRS LISS) for both floods

The good results from this pilot project will continue in a new project which to cover the whole Sofia Valey and all the main rivers which passes through it.

For more information:
Remote Sensing Application Center – ReSAC